Arsenic can be naturally present or can be related to agricultural or industrial activities.  Arsenic was an element in pesticides used in apple orchards; it was used in pressure treated lumber and in paints used to hinder the growth of barnacles on boats.  Most commercial uses of arsenic have been banned.  In most cases of arsenic contamination of drinking water it is difficult to distinguish whether it is man-made or natural.  However, studies of the geology of New Hampshire show that the arsenic found in our drinking water is commonly present naturally.

Arsenic in water has no taste or odor.  The only way to know if it is present is to test.

Long-term ingestion of arsenic is been linked to cancers, cardiovascular disease, immunological disorders, skin problems, diabetes and neurological issues.  The EPA standard for arsenic is .010 milligrams per liter (mg/L), which is the same as 10 micrograms per liter (ug/L), also known as parts per billion. The maximum contaminant level goal (MCLG) is zero.

In 2000 the EPA and Congress lowered the standard for arsenic from .050 mg/L to .010 mg/L.  This was in recognition of the long term health issues caused by ingestion of arsenic.  Arsenic is described as an “accumulative enabler” as long-term exposure can lead to disease over time.

Arsenic is present in two chemical forms, Arsenic +3 (arsenite) and Arsenic +5 (arsenate).  All treatment methods are more effective on Arsenic +5.  The breakdown in valence of a particular water supply will be changeable, however, in NH our waters tend to have 20-30% arsenite.

When choosing a treatment plan the first decision that must be made is whether to treat the drinking water only or the whole house or facility water source.  Research on the effects of bathing exposure has been inconclusive, but indicates that the predominance of the health issues associated with arsenic come from drinking.

Ways to treat for Arsenic

1.  "Point of Use" treatment in the Kitchen

For extremely low levels of arsenic, a cartridge style filter can be installed to treat water for a separate tap in the kitchen.  This is the least expensive method but has a major drawback in that the cartridge has a finite life and there is no way to know when it stops working.  Homeowners tend to forget to change the cartridge and therefore may believe they are being protected, when in fact they are not.  

A more robust approach uses reverse osmosis (RO) technology with the system located either under the kitchen sink or in the basement below the kitchen.  The treated water is plumbed to a separate tap at the sink (designer finishes are available) and can also be hooked up to the refrigerator.  RO will remove 80 to 95% of arsenate and 60 to 70% of arsenite.  When further removal is desired, a cartridge of a specialty media can be added after the RO system.  In rare cases where arsenic is extremely high, a booster pump can be added ahead of the RO, improving its performance. 
 
2.  “Point of Use” treatment at all major drinking water locations.

RO systems can be installed for bathrooms as well as kitchens.  If two bathrooms share a wall, one system can be plumbed to serve both locations.

POINT of ENTRY TREATMENT - "POE"

Point of entry treatment can be installed when arsenic reduction throughout the home is desired.  Because it is more difficult to ensure consistent below detection arsenic when the entire water stream is being treated, we recommend that a drinking water system for the kitchen is also installed when “POE” treatment is chosen.  This level of redundancy assures that even with mechanical or water chemistry fluctuations, the family will be drinking water that does not pose a health risk from arsenic.

3.   "Point of entry" system, adsorption

Many medias are available that can reduce arsenic through adsorption.  These materials are installed in fiberglass tanks, with a “lead-lag” two tank configuration being the most robust.  The lead-lag configuration provides extra protection and allows a sampling point between the two tanks, allowing for monitoring and detection before any arsenic has made it into the household water.  In some cases pretreatment is recommended or required.  Because of the way arsenic behaves, it may not be possible to attain “non-detectable” arsenic, and in all cases the capacity of the media will eventually be exhausted.  At this point the media should be replaced and the tanks rebedded with fresh media.  Because of this, ongoing testing (at least once per year) is important and is the homeowner’s responsibility.  This testing will determine the timing of rebedding.

4.  "Point of entry" system, anion exchange

A special water softener resin, called anion resin, can be used to remove arsenate.  (Anion resin is not effective on arsenite.)  This system is able to regenerate itself, flushing the arsenic to drain, so the long term cost is less than adsorption.  A post treatment step of neutralization may be required as anion exchange can make the water more corrosive to the plumbing.  The anion exchange system can then be followed by an adsorption system; the presence of the anion will greatly increase the life of the adsorption media.  

5.  "Point of Entry" system, with oxidation